Field of the Invention
The invention pertains to a device and a method for measuring a temperature of a support rotating with predetermined angular velocity about a rotational axis. At least one temperature sensor is thermally coupled to the support, and a measurement configuration which is assigned to the at least one temperature sensor may be coupled with an electronic evaluation circuit.
In the epitaxial coating of semiconductor wafers, control of the epitaxial growth process requires precise regulation, or at least knowledge, of the temperature of the support plate on which the semiconductor wafer is placed. The temperature of the rotating epitaxy wafer support plate is conventionally measured with pyrometric measuring methods. These processes, however, often lead to false measurement results because of the variable color coefficient of the surface of the support or of the epitaxially applied layers. Since the temperature of the epitaxy wafer has an important effect on the growth process of this wafer, and the wafer temperature is coupled with the temperature of the support plate substantially via the gas used in the epitaxy method and results merely to a lesser extent from the exchange of radiation energy, the actual temperature of the support plate can be recorded only indirectly when pyrometric measurements are used. More accurate measurement results are given by direct thermometric methods, in which a temperature-dependent resistor (for example a 1 k.OMEGA. platinum wire resistor) is imbedded in the support plate, with its connections routed via a ceramically insulated wire to a slip ring on the rotational shaft. However, because of the comparatively high temperatures to be measured, difficulties arise with a measurement configuration of this type when trying to achieve a permanently reliable electric contact. A further secondary condition which generally applies in systems of this type is that no materials which, at the high usual operating temperatures of generally more than 500.degree. C. release even a small amount of gases, should be introduced into the reactor space along with the means for measuring the temperature of the wafer support plate. This means that the gas pressure of the measuring means that are used must be extremely low even at high temperatures.